T cells play a pivotal role in the regulation of immune responses and are important for establishing immunity to pathogens. In addition, T cells are often activated during inflammatory autoimmune diseases, such as rheumatoid arthritis, inflammatory bowel disease, type I diabetes, multiple sclerosis, Sjogren's disease, myasthenia gravis, psoriasis, and lupus. T cell activation is also an important component of organ transplantation rejection, allergic reactions, and asthma.
T cells are activated by specific antigens through T cell receptors (TCR), which are expressed on the cell surface. This activation triggers a series of intracellular signaling cascades mediated by enzymes expressed within the cell (Kane, L P et al. Current Opinion in Immunol. 2000, 12, 242). These cascades lead to gene regulation events that result in the production of cytokines, including interleukin-2 (IL-2). IL-2 is a critical cytokine in T cell activation, leading to proliferation and amplification of specific immune responses.
Kinase enzymes have been shown to be important in the intracellular signal transduction. One class of kinase enzymes involved in signal transduction is the Src-family of protein tyrosine kinases (PTK's), which includes, for example: Lck, Fyn(B), Fyn(T), Lyn, Src, Yes, Hck, Fgr and Blk (for review see: Bolen, J B and Brugge, J S Annu. Rev. Immunol 1997, 15, 371). Gene disruption studies suggest that inhibition of some members of the Src family of kinases would potentially lead to therapeutic benefit. Src(−/−) mice have abnormalities in bone remodeling or osteopetrosis (Soriano, P. Cell 1991, 64, 693), suggesting that inhibition of the src kinase might be useful in diseases of bone resorption, such as osteoporosis. Lck(−/−) mice have defects in T cell maturation and activation (Anderson, S J et al. Adv. Immunol. 1994, 56, 151), suggesting that inhibition of the Lck kinase might be useful in diseases of T cell mediated inflammation. In addition, human patients have been identified with mutations effecting Lck kinase activity (Goldman, F D et al. J. Clin. Invest. 1998, 102, 421). These patients suffer from a severe combined immunodeficiency disorder (SCID).
Src-family kinases are also important for signaling downstream of other immune cell receptors. Fyn, like Lck, is involved in TCR signaling in T cells (Appleby, M W et al. Cell 1992, 70, 751). Hck and Fgr are involved in Fcγ receptor signaling leading to neutrophil activation (Vicentini, L. et al. J. Immunol. 2002, 168, 6446). Lyn and Src also participate in Fcγ receptor signaling leading to release of histamine and other allergic mediators (Turner, H. and Kinet, J-P Nature 1999, 402, B24). These findings suggest that Src family kinase inhibitors may be useful in treating allergic diseases and asthma.
Src kinases have also been found to be activated in tumors including sarcoma, melanoma, breast, and colon cancers suggesting that Src kinase inhibitors may be useful anti-cancer agents (Abram, C L and Courtneidge, S A Exp. Cell Res. 2000, 254, 1). Src kinase inhibitors have also been reported to be effective in an animal model of cerebral ischemia (R. Paul et al. Nature Medicine 2001, 7, 222), suggesting that Src kinase inhibitors may be effective at limiting brain damage following stroke.
Cancer is the second leading cause of death in the United States (Boring, et al., CA Cancer J. Clin., 43:7, 1993), and features uncontrolled cellular growth, which results either in local invasion of normal tissue or systemic spread (metastasis) of the abnormal growth. Cancer is caused by inherited or acquired mutations in cancer genes, which have normal cellular functions and which induce or otherwise contribute to cancer once mutated or expressed at an abnormal level. Certain well-studied tumors carry several different independently mutated genes, including activated oncogenes and inactivated tumor suppressor genes. Each of these mutations appears to be responsible for imparting some of the traits that, in aggregate, represent the full neoplastic phenotype (Land et al., Science, 222:771, 1983; Ruley, Nature, 4:602, 1983; Hunter, Cell, 64:249, 1991).
One such trait is gene amplification. Gene amplification involves a chromosomal region bearing specific genes undergoing a relative increase in DNA copy number, thereby increasing the copies of any genes that are present. In general, gene amplification results in increased levels of transcription and translation, producing higher amounts of the corresponding gene mRNA and protein. Amplification of genes causes deleterious effects, which contribute to cancer formation and proliferation (Lengauer et al. Nature, 396:643-649, 1999). Gene amplification has been established as an important genetic alteration in solid tumors (Knuutila et al., Am. J. Pathol., 152(5):1107-23, 1998; Knuutila et al., Cancer Genet. Cytogenet., 100(1):25-30, 1998).
Another trait of tumor cells is the over-expression or differential expression of whole collections of genes. In pre-cancerous or cancerous cells, and tissues, where both amplification of a gene and over-expression of the gene product occur, then that gene and its product present both a diagnostic target as well as a therapeutic opportunity for intervention. In many cases, the amplified cancer genes encode an enzyme, such as a kinase, and the discovery and characterization of inhibitors of the enzymatic activity of this gene product will be a promising avenue that leads to novel therapeutics for cancer treatment.
ACK1 is a gene that is frequently amplified and over-expressed in primary human tumors (U.S. Patent Publication No. 20030175763). ACK1 kinase activity is regulated in the context of cell attachment and detachment, and certain cancer cells depend on ACK1's kinase activity for adhesion, anchorage independent growth and survival. Down regulation of ACK1 kinase activity or ACK1 expression levels can result in reduced tumor growth in animal models. Accordingly, Ack is a target believed to be useful in the regulation of cancer.
The ACK1 gene encodes an intracellular, non-receptor tyrosine kinase that binds cdc42Hs in its GTP-bound form and inhibits both the intrinsic and GTPase-activating protein (GAP)-stimulated GTPase activity of p21cdc42, a Ras-like protein involved in cell growth (Manser et al., Nature 363(6427): 364-367, 1993). This binding is mediated by a unique polypeptide of 47 amino acids C-terminal to an SH3 domain. ACK1 gene contains a tyrosine kinase domain and is reported to possess tyrosine kinase activity. The protein may be involved in a regulatory mechanism that sustains the GTP-bound active form of cdc42Hs and which is directly linked to a tyrosine phosphorylation signal transduction pathway.
While various groups have published on inhibitors of Src family kinase or ACK-1, disclosing various chemical compounds, including 2-phenylamino-imidazo[4,5-h]isoquinolin-9-ones (Snow, R J et al. J. Med. Chem. 2002, 45, 3394), pyrazolo [3,4-d]pyrimidines (Burchat, A F et al. Bioorganic and Med. Chem. Letters 2002, 12, 1987 and Hanke, J H et al. J. Biol. Chem. 1996, 271, 695), pyrrolo [2,3-d]pyrimidines (Altmann, E et al. Bioorganic and Med. Chem. Letters 2001, 11, 853), anilinoquinazolines (Wang, Y D et al. Bioorganic and Med. Chem. Letters 2000, 10, 2477), and imidazoquinoxalines (Chen, P. et al. Bioorganic and Med. Chem. Letters 2002, 12, 3153), none of these groups describe the compounds of the present invention, and particularly as modulators of kinase enzymes such as Lck and ACK-1, and useful for the regulation of T-cell mediated immune response, autoimmune disease, organ transplantation, allergies, asthma, cancer and the like.